Photographic colloid transfer process with a sulfur dioxide adduct tanning developer



M r 8, 1967 P. B. GILMAN. JR.. ETAL 3,

PHOTOGRAPHIC COLLOID TRANSFER PROCESS WITH A SULFUR DIOXIDE ADDUCT TANNING DEVELOPER Filed Aug. 23, 1965 l REFLEX EXPOSURE E 1 a UNHARDENED A x EMULSION n /r.-'.-,-' commmrfe 'mNNnNe DEVELOPING AGENTAND SILVER l0 PRECIPITATING AGENT ALKALI DEVELOPMENT UNHARD ENEDl HARDENED JohnG. Barnes Paul B. Gillnanfi' INVENTOR.

BY M

United States Patent 3,311,472 PHOTOGRAPIHC COLLOID TRANSFER PROCESS WiTH A SULFUR DIOXIDE ADDUCT TANNING DEVELOPER Paul B. Gilman, Jr., and John C. Barnes, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Aug. 23, 1963, Ser. No. 304,139 13 Claims. (Cl. 9628) This invention concerns a colloid transfer process of making multiple copies photographically.

It is well known to use the colloid transfer process particularly for oh'ice copying purposes to make multiple copies by exposing a substantially unhardened silver halide emulsion containing a tanning developer and a non-tanning developer to an image followed by activation in an alkaline solution. Typical processes are described in Yutzy et al. US. 'Patents 2,596,756 and 2,716,059. The exposed and developing emulsion is contacted against a receiver sheet whereby a stratum of partially developed and unhardened silver halide emulsion is transferred to the receiving sheet. Contacting with successive receiving sheets results in the transfer of successive receiving sheets results in the transfer of successive layer so that several copies can be prepared. However, due to the presence of a gelatin-tanning silver halide developer in the emulsion, the number of copies which can be transferred depends upon the speed with which the transfers are made due to hardening of the unexposed areas by the tanning developer. Therefore, it has been desired to find a process which will enable successive copies to be made by the colloid transfer process, which would enable the transfers to be made at a slower rate and also which would permit more copies to be made from a single emulsion.

We have found a method of providing a colloid transfer photographically which results in a larger number of copies being made, which avoids the necessity for speed in the transferring operation and provides an immediate permanent dark silver image.

One object of this invention is to provide a colloid transfer process which provides a larger number of copies than has been possible in previously known processes. Another object is to provide a colloid transfer process which is independent of the speed of the transfer operation to obtain a large number of copies. A further object is to provide a colloid transfer process in which the emulsion can be dried following the transfer of a few copies and then remoistened to make additional copies. A further object is to provide a colloid transfer silver halide emulsion containing incorporated physically developable nuclei.

The above objects are attained by the use of a silver halide emulsion containing a watensoluble silver halide tanning developer made by forming the sulfur dioxide adduct of the developer. A silver precipitating agent such as silver proteinate is also incorporated in the emulsion. This emulsion is coated on a suitable support, exposed to an image and then developed in an alkaline activator solution containing a silver halide solvent such as sodium thiosulfate. The developed emulsion can then be pressed in contact against a receiving surface such as a paper sheet in succession to form multiple copies of the unexposed silver halide, a stratum of which transfers upon each contacted support.

Operation of the process depends upon the use of a substantially unhardened emulsion such as the type disclosed in Yutzy et al. US. Patents 2,596,756 and 2,716,059, wherein the emulsion layer is not harder than would be the case with gelatin containing 0.25 ounce of formaldehyde (40% diluted 1:3 with water); or 0.7 gram of dry formaldehyde per pound when freshly coated; or 0.1 ounce of the solution per pound for a sample aged 3 to 6 months.

Tanning developing agents especially useful because of their water solubility characteristics in emulsion layers are sulfur dioxide adducts of tanning developers, for example, toluhydroquinone, 1-phenyl-4,4-dimethyl-3-pyrazolidone-hydroquinone mixture, Elon (N methyl paminophenol sulfate)-hydroquinone mixture, chlorohydroquinone, pyrogallol monocarbonate, nordihydroguairetic acid, gentisic acid, catechol carbonate, etc. The catechol sulfur dioxide adduct is a particularly useful tanning developer since it is satisfactorily water-soluble and tans gelatin mainly at the emulsion surface. A mixture of these containing two or more may also be used.

Preparation of S0 adducts is disclosed in an article entitled Clathrates in Chemical Reviews, published by the American Chemical Society, Washington, DC, volume 59, pages 827830, October 1959;

Suitable water-soluble silver halide tanning developers must have adequate stability to provide for storing the silver halide emulsion without fogging the emulsion or tanning the emulsion during storage.

The concentration of tanning developing agent in the emulsion is dependent in part upon the result desired, but a useful range is of the order of .01 to .10 mole of developing agent per mole of silver nitrate converted to silver halide, used in making the emulsion.

Since it is desirable that the stratum of the emulsion obtained on the receiving sheet have sufficient optical density that it is immediately visible, colored matter or pigments may be initially incorporated in the emulsion lay-er before exposure or subsequently as formed in the stratum of the transferred emulsion layer. For instance, heating may be employed to accelerate development of the silver halide in the transferred stratum or a fogging agent such as thiourea or the like may be incorporated on the surface of the receiving sheet. For certain purposes, it

may be desirable to incorporate a color developingagent in the emulsion which will provide density to the transferred stratum.

Although it is preferred to use a paper support for the silver halide emulsion and for the receiving sheet, it will be appreciated that other supports can be used for both purposes such as those made from cellulose derivatives including cellulose acetate and the like, other polymeric materials such as polyethylene terephthalate, polyethylene, polystyrene and the like, glass, wood, etc., including those which are customarily known as supports for photographic emulsions.

Silver chloride is a particularly useful silver halide for use in this process but other silver halides may be used including silver bromide, silver iodide, silver chlorobromide, silver chloroiodide, silver bromoiodide, silver chlorobrornoiodide, and the like.

The silver precipitating agents comprise insoluble photographic physical development nuclei including colloidal silver, colloidal gold, silver oxide, silver proteinate, cobalt sulfide, zinc sulfide, cadmium sulfide, nickel sulfide, etc. A mixture of two or more may also be used.

A useful coating of the photographic emulsion in this process comprises .003 to .015 mole silver halide per square foot, .001 to .005 gram nuclei per square foot and .01 to .10 mole of water-soluble tanning developing agent per mole of silver halide in the emulsion.

The activator solution can be any of the well-known activator solutions such as those containing sodium carbonate and urea, provided that a silver solvent is also present therein. Suitable silver halide solvents in addition to sodium thiosulfate include sodium thiocyanate, sodium sulfite, etc.

Toners of the type used in the difiusion transfer systems may be used advantageously to improve the darkness of the image obtained according to our invention. Typical toners are described in Tregillus et al. U.S. Patent 3,017,270, issued January 16, 1962. However, other toners which are known in the art can be used.

A variety of hydrophilic organic colloid vehicles can be used for the silver halide emulsions provided they can be tanned or hardened using silver halide tanning type developers. These colloid vehicles include proteins such as gelatin, soy bean protein, casein, and the like,

as well as synthetic organic colloids which are hydrophilic, such as polyvinyl alcohol, hydrolized cellulose esters, etc. It will also be appreciated that mixtures of these colloids are intended within the term, tan-nable hydrophilic organic colloid.

It will be appreciated that the preparation of lightsensitive silver halide emulsions and the development thereof are carried out under appropriate safe-light conditions.

The accompanying drawings show one embodiment of the invention.

As shown in FIG. 1, the subject 12 and emulsion layer 11, are arranged and exposed. The amount of exposure depends, of course, upon a number of factors such as the contrast of the subject, the emulsion sensitivity and light source and should be regulated so that the regions corresponding to the shadows of the subject are not unduly exposed. Exposure results in partially and uniformly exposing the emulsion with the light coming through the support whereby latent images are obtained in both areas 13 and 14 corresponding to the shadows and highlight region respectively, the relative amount of latent images obtained in these areas of the emulsion layer being dependent somewhat upon the contrast of the subject. With proper selection of exposure time, when the exposed element is developed at 80 F., sufficiently with an alkaline solution such as percent carbonate solution containing 3 percent urea and 1 percent sodium thiosulfate, the result is to form silver throughout the emulsion layer as shown in FIG. 2 of the drawings, partly due to the image exposure and partly due to the general exposure through the support. In region 16 of the emulsion layer, since exposure is less, and therefore hardening is less, the region will transfer, whereas in region of a greater exposure, the emulsion is hardened sufficiently during development to prevent its transfer. It is preferred to have urea, salicylic acid, or other gelatin softeners in the alkaline developer solutions to facilitate transfer of a stratum of unhardened emulsion. Urea and other softeners such as formamide, ethylene chlorohydrin, sodium nitrate and the like can be used in the alkaline developer solution or in a separate solution following development, in concentrations of the order of 220 percent, to accommodate variations which may be encountered in different emulsions and condition of development.

The developed element of FIG. 2 may then be wiped or squeegeed to remove excess moisture and then pressed with the emulsion side next to an absorbent sheet such as paper 17 with the result that the unhardened resin 16 adheres to the sheet and when the sheet is peeled off, only a thin stratum 18 of region 16 remains on the sheet as shown in FIG. 3. Additional copies of the subject can be made by merely remoistening the emulsion layer 11 with alkaline solution and making transfers to the sheets until the unhardened region 16 is exhausted.

The following examples are intended to illustrate our invention but not to limit it in any way.

Example 1 A silver chloride emulsion containing 1 mole of silver and 64 grams of gelatin in 920 grams of emulsion was diluted as follows:

Silver chloride emulsion 150 10% bone gelatin 250 H O 50 After the above blend was made, 4 ml. of a catechol solution (made by dissolving 5 grams of catechol in 50 grams of distilled water followed by saturation with gaseous sulfur dioxide) was added to ml. of the diluted emulsion, then coated 0.010 inch, wet thickness on cellulose acetate support. Prior to coating, 1 to 3 ml. of a silver proteinate solution containing 1 gram of silver proteinate (Mallinclcrodt) per liter of 2 percent gel was added to the 90 ml. of incorporated developer emulsion melt.

When an activater composed of Sodium carbonate grams S0 Urea do 30 Sodium thiosulfate --do 14 Distilled water liters 1 was used at 80 F. for 1 minute, a good tanning differential was obtained: Seventeen copies with immediate dark images transferred in the unexposed areas to paper receiving sheets.

The above example is repeated using physical development nuclei substituted for silver protei-nate. Colloidal silver, colloidal gold, silver oxide, cobalt sulfide, zinc sulfide and nickel sulfide also produce satisfactory results.

The above example is repeated substituting the following developers for catechol, with similar results: toluhydroquinone, l-phenyl-4,4-dimethyl-3-pyrazolidonehydroquinone mixture, Elon-hydroquinone mixture, chlorohydroquinone, pyrogallol monocarbonate, catechol, catechol carbonate, nordihydroguairetic acid and gentisic acid. The incorporated developer solution need not be incorporated directly in the emulsion preparation but may be coated as a separate layer underneath the light-sensitive layer.

Omission of the physical development nuclei requires an involved processing cycle in order to obtain a satisfactory neutral tone image in the transferred copies. However, the copies can be made successively without having the short time requirement of previously known colloid transfer processes.

Example 2 To prepare a water-soluble developer solution suitable for incorporation in a silver halide emulsion sulfur dioxide gas is bubbled into a hydroxy alkyl amine such as Z-diethylaminoethanol until at least 0.5 mole of sulfur dioxide have reacted with 1 mole of the amine so that an acidic solution results.

To 50 grams of the amine-sulfur dioxide complex is added 1.0 gram of 4,4-dimethyl-3-pyrazolidone and 10 grams of hydroquinone. A medium speed sliver bromoiodide emulsion containing 1 mole of silver and 64 grams of gelatin in 0.62 kilogram of emulsion is coated after making the following additions to grams of the melted emulsion; 250 g. of 10 percent gelatin, 100 g. of distilled water and 1.0 g. of the developer-hydroxy alkyl amine-S0 solution. The emulsion mixture is coated .010 inch, wet thickness on cellulose acetate or paper support.

The coated emulsion is exposed to light using the image to be copied as a pattern in such manner as to form a negative latent image in the emulsion.

The sheet is treated with a solution of 5 percent sodium carbonate to activate the incorporated developing agents and cause development of a negative silver image. In the exposed areas containing the developing silver the gelatin becomes hardened or insolubilized, while the gelatin in areas which were not exposed remains relatively unaffected.

The developed emulsion is then pressed in contact with an absorbent receiving sheet and stripped off, leaving a dense brown image of good quality and excellent definition adherent to the receiving sheet. The coated sheet may then immediately be reapplied to additional receiving sheets in a similar manner and successive transfers accomplished merely by repeating the contact and stirpping operation.

The images thus formed appear to contain very little gelatin and the sensitized sheet shows little evidence of the removal of a layer of gelatin. After many transfers have been made, the transferring surface of the sensitized sheet appears to be composed of very minute random pits as though gelatin were being removed in the form of minute capsules. The fact that the original brown images can be darkened by exposure to light or chemical reduction, indicates that the transferred material contains silver halide. Since many successive halftone images can be transferred, it appears that the amount of gelatin transferred must be very small, for otherwise, the dot pedestal structure would be rapidly removed. The transferred dot image does not increase in size during the transfer of more than 60 copies. It is possible to make successive high contrast transfers of continuous tone images.

To improve the blackness of the transfer image the following processing cycle was used:

(1) Exposure (2) One minute activation in 5 percent sodium carbonate (3) Ten second water rinse (4) Flash to a 100-watt lamp at a distance of 2 feet for seconds (5) Develop in Kodak Developer D72 (6) Wash for 1 minute When the above treated matrix was placed on a Ditto machine, over 100 good gelatin transfer images could be obtained with only water in the fountain which normally contains an aqueous dye solution.

Example 3 A developer solution suitable for incorporation in a silver halide emulsion but not requiring the use of an hydroxy alkyl amine is prepared by dissolving 5 grams of catechol in 50 grams of distilled water and adding 1.6 grams of gaseous sulfur dioxide by bubbling the gas into the solution.

An emulsion coating was prepared by adding 50 ml. of distilled water and 250 grams of 10 percent calfskin gelatin to 100 grams of a pure silver chloride emulsion which contained one mole of silver and 64 grams of gelatin in 0.62 kilogram of emulsion. To 90 ml. of this diluted emulsion was added 4 ml. of the catechol-sulfur dioxide solution, and the mixture coated 0.010 inch thick on cellulose acetate support.

The method of processing and results were the same as for Example 2.

Other water-soluble developing agents substituted for catechol are: toluhydroquinone, a mixture of 4,4-dirnethyl- 3-pyrazolidone and hydroquinone, a mixture of Elon and hydroquinone, chlorohydroquinone, pyrogallol monocarbonate, catechol carbonate, nordihydroguairetic acid and gentisic acid.

It will be appreciated that the stratum of emulsion which is transferred to the hydrophilic surface can be used as a lithographic printing plate by inking the image with greasy printing ink. It is also helpful to treat the G image with known treating agents to further improve the difference in affinity for the greasy printing ink between the image area and the support. A typical treating agent is disclosed in Lake et al. US. Patent 2,794,388.

The invention has been described in detail with partic ular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A light sensitive substantially unhardened gelatinosilver halide emulsion on a support, said emulsion containing at least one water soluble gelatin tanning silver halide developing agent comprising a sulfur dioxide adduct of a gelatin tanning silver halide developer.

2. A composition of claim 1 in which the emulsion contains physical development nuclei.

3. A composition of claim 1 in which the emulsion contains physical development nuclei and in which the said water soluble gelatin tanning silver halide developing agent is selected from the class consisting of toluhydroquinone, 1 phenyl-4,4-dimethyl-3-pyrazolidone-hydroquinone mixture, N-methyl-p-aminophenol sulfate-hydroquinone mix ture, chlorohydroquinone, pyrogallol monocarbonate, catechol, catechol carbonate, nordihydroguairetic acid and gentisic acid.

4. A composition of claim 1 in which the emulsion contains at least one nuclei selected from the class consisting of colloidal silver, colloidal gold, silver oxide, silver pro-.

teinate, cobalt sulfide, zinc sulfide, and nickel sulfide.

5. A light sensitive substantially unhardened gelatinosilver halide emulsion on a support, said emulsion having in contiguity therewith a Water soluble gelatin tanning silver halide developing agent comprising the sulfur di- OXide adduct of a gelatin tanning silver halide developer.

6. A composition of claim 5 in which the emulsion con tains physical development nuclei.

7. A method of photographic reproduction which comprises developing an exposed substantially unhardened gelatino-silver halide emulsion layer on a support, said emulsion containing at least one Water soluble gelatin tanning silver halide developing agent comprising a sulfur dioxide adduct of a gelatin tanning silver halide developer, with an alkaline solution to obtain a hardened gelatin and chemically developed silver image in the image areas and substantially unhardened gelatin, physically developed silver and silver halide in the region of the emulsion layer corresponding to the unexposed areas and removing the substantially unhardened gelatin areas from the said support.

8. A method of claim 7 in which the unhardened gelatin areas are removed by pressing a receiving surface against said emulsion layer while said emulsion layer is moist to cause only the unhardened region of the emulsion to adhere to said surface and separating said surface and emulsion layer to transfer only a stratum of said unhardened region of the emulsion layer to said surface.

9. A method of claim 7 in which the emulsion contains physical development nuclei.

10. A method of claim 7 in which the gelatino-silver halide tanning developing agents are selected from the class consisting of toluhydroquinone, l-phenyl-4,4-dimethyl-3- pyrazolidone-hydroquinone mixture, N-methyl-p-aminophenyl sulfate-hydroquinone mixture, chlorohydroquinone, pyrogallol monocarbonate, catechol, catechol carbonate, nordihydroguairetic acid and gentisic acid.

11. A method of photographic reproduction which oomprises developing an exposed substantially unhardened gelatino-silver halide emulsion on a support, said emulsion having in contiguity therewith at least one water soluble gelatinosilver halide developing agent comprising the sulfur dioxide adduct of a gelatin tanning silver halide developer, with an alkaline solution to obtain a hardened gelatin and chemically developed silver image in the image areas and substantially unhardened gelatin corresponding to the non-image areas and removing the unhardened gelatin areas.

12. A method of claim 11 in which the emulsion layer contains physical development nuclei.

13. A method of claim 11 in which the unhardened gelatin areas are removed by pressing a receiving surface against said emulsion layer while said emulsion layer is moist to cause only the unhardened areas of the emulsion to adhere to said surface and separating said surface and emulsion layer to transfer only a stratum of said unexposed region of the emulsion layer to said surface.

No references cited.

NORMAN G. TORCHIN, Primary Examiner.

J. TRAVIS BROWN, Examiner.

" J. H. RAUBITSCHEK, Assistant Examiner. 

7. A METHOD OF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES DEVELOPING AN EXPOSED SUBSTANTIALLY UNHARDENED GELATINO-SILVER HALIDE EMULSION LAYER ON A SUPPORT, SAID EMULSION CONTAINING AT LEAST ONE WATER SOLUBLE GELATIN TANNING SILVER, HALIDE DEVELOPING AGENT COMPRISING A SULFUR DIOXIDE ADDUCT OF A GELATIN TANNING SILVER HALIDE DEVELOPER, WITH AN ALKAINE SOLUTION TO OBTAIN A HARDENED GELATIN AND CHEMICALLY DEVELOPED SILVER IMAGE IN THE AREAS AND SUBSTANTIALLY UNHARDENED GELATIN, PHYSICALLY DEVELOPED SILVER AND SILVER HALIDE IN THE REGION OF THE EMULSION LAYER CORRESPONDING TO THE UNEXPOSED AREAS AND REMOVING THE SUBSTANTIALLY UNHARDENED GELATIN AREAS FROM THE SAID SUPPORT. 